Wheel constructions for agricultural vehicles and the like off-road vehicles, are known which include a circular wheel rim which provides respective axially inner and outer flanges which each provide a seat for a tyre bead of a floatation tyre which is fitted to a radially outer, or “tyre side” of the rim. In the example of U.S. Pat. No. 5,560,686, such a wheel construction is disclosed which further includes a disc by means of which the wheel is securable to a hub of the vehicle, the disc being connected to a radially inner side of the rim and the disc and rim being separable. The invention is also applicable to wheels in which the rim and disc are permanently connected together e.g. by welding.
In this specification, by “floatation tyre” we mean a wide (axially long) tyre which spreads loads thus reducing, e.g. soil, compaction, when the tractor is driven on a non-road surface.
Agricultural vehicle wheel constructions 110 are known, such as the one illustrated in FIG. 3, which include a wheel rim 111 with axially inner and outer portions 115 which each provide a tyre bead seat flange 122, and an adjoining frusto-conical connecting surface 123 which extends axially towards the mid-portion 118 where there is a central well. The tyre bead seat flange 122, and typically at least a part of the connecting surface 123, together provide a seat for the tyre 114. The connecting surface 123 adjoins a circumferentially extending convex surface 126, and a frusto-conical side part 120, 128 adjoins the convex surface 126, and the mid-portion 118 of the rim 111.
It has been found that with such existing rims, the service life of the rims may be insufficient because structural stresses which occur in the area where the side parts adjoin the mid-region, can lead to premature failures of the rims.